Add test to provider test suite that provider source does not rely

on source layer or provider in any way

Fails for OGR provider! :o

python/core/qgsfeaturerequest.sip

@@ -343,7 +343,7 @@ class QgsAbstractFeatureSource
      * @param request The request
      * @return A feature iterator
      */
-    virtual QgsFeatureIterator getFeatures( const QgsFeatureRequest& request ) = 0;
+    virtual QgsFeatureIterator getFeatures( const QgsFeatureRequest& request = QgsFeatureRequest() ) = 0;
 
   protected:
     void iteratorOpened( QgsAbstractFeatureIterator* it );

python/core/qgsvectorlayerfeatureiterator.sip

@@ -2,6 +2,23 @@
 // abstract feature iterator implementations are not part of public API
 
 
+class QgsVectorLayerFeatureSource : QgsAbstractFeatureSource
+{
+%TypeHeaderCode
+#include <qgsvectorlayerfeatureiterator.h>
+%End
+  public:
+
+    /** Constructor for QgsVectorLayerFeatureSource.
+     * \param layer source layer
+     */
+    explicit QgsVectorLayerFeatureSource( const QgsVectorLayer *layer );
+
+    ~QgsVectorLayerFeatureSource();
+
+    virtual QgsFeatureIterator getFeatures( const QgsFeatureRequest &request = QgsFeatureRequest() );
+};
+
 class QgsVectorLayerFeatureIterator : QgsAbstractFeatureIterator
 {
 %TypeHeaderCode

src/core/qgsfeaturerequest.h

@@ -437,7 +437,7 @@ class CORE_EXPORT QgsAbstractFeatureSource
      * \param request The request
      * \returns A feature iterator
      */
-    virtual QgsFeatureIterator getFeatures( const QgsFeatureRequest &request ) = 0;
+    virtual QgsFeatureIterator getFeatures( const QgsFeatureRequest &request = QgsFeatureRequest() ) = 0;
 
   protected:
     void iteratorOpened( QgsAbstractFeatureIterator *it );

src/core/qgsvectorlayerfeatureiterator.h

@@ -36,7 +36,6 @@ class QgsVectorLayerFeatureIterator;
 
 /** \ingroup core
  * Partial snapshot of vector layer's state (only the members necessary for access to features)
- * \note not available in Python bindings
 */
 class CORE_EXPORT QgsVectorLayerFeatureSource : public QgsAbstractFeatureSource
 {
@@ -49,7 +48,7 @@ class CORE_EXPORT QgsVectorLayerFeatureSource : public QgsAbstractFeatureSource
 
     ~QgsVectorLayerFeatureSource();
 
-    virtual QgsFeatureIterator getFeatures( const QgsFeatureRequest &request ) override;
+    virtual QgsFeatureIterator getFeatures( const QgsFeatureRequest &request = QgsFeatureRequest() ) override;
 
     friend class QgsVectorLayerFeatureIterator;
 

tests/src/python/providertestbase.py

@@ -24,6 +24,7 @@ from qgis.core import (
     QgsExpressionContextScope,
     QgsExpressionContext,
     QgsVectorDataProvider,
+    QgsVectorLayerFeatureSource,
     NULL
 )
 
@@ -477,6 +478,30 @@ class ProviderTestCase(object):
         values = [f['pk'] for f in self.vl.getFeatures(request)]
         self.assertEqual(values, [5, 4, 3, 2, 1])
 
+    def testOpenIteratorAfterLayerRemoval(self):
+        """
+        Test that removing layer after opening an iterator does not crash. All required
+        information should be captured in the iterator's source and there MUST be no
+        links between the iterators and the layer's data provider
+        """
+        if not getattr(self, 'getEditableLayer', None):
+            return
+
+        l = self.getEditableLayer()
+        self.assertTrue(l.isValid())
+
+        # store the source
+        source = QgsVectorLayerFeatureSource(l)
+
+        # delete the layer
+        del l
+
+        # get the features
+        pks = []
+        for f in source.getFeatures():
+            pks.append(f['pk'])
+        self.assertEqual(set(pks), {1, 2, 3, 4, 5})
+
     def testGetFeaturesFidTests(self):
         fids = [f.id() for f in self.provider.getFeatures()]
         assert len(fids) == 5, 'Expected 5 features, got {} instead'.format(len(fids))